This invention relates to methods of forming semiconductive active area having a proximity gettering region and to methods of processing monocrystalline silicon substrates to have a proximity gettering region.
Impurity contamination of active area semiconductive materials is a problem within the semiconductor industry. Of particular concern are metallic contaminants, such as iron, nickel and copper. When such impurities are present in semiconductive material of a device, the impurities can degrade the characteristics and reliability of the device. As integration in semiconductor devices becomes increasingly dense, the tolerance for metallic contaminants becomes increasingly stringent.
Among the methods for decreasing metallic contamination in semiconductor wafers are methods for improving cleanliness in plants which manufacture such semiconductive devices. However, regardless of how many steps are taken to insure clean production of semiconductor devices, some degree of contamination by metals seems inevitable. Accordingly, it is desirable to develop methods and structures for isolating metallic contaminants present in semiconductor wafers from devices which are ultimately formed within and upon such wafers. The act of isolating these contaminants is generally referred to as gettering, as the contaminants are gathered (typically physically and/or chemically), or gettered, to specific areas (referred to as xe2x80x9cproximity gettering regionsxe2x80x9d) within a semiconductor wafer.
Conventional processes for gettering metallic contaminants often focus on creating defects or damage within a semiconductor wafer in a region where gettering is sought to occur. Generally, such gettering regions are at least formed within active area of the substrate below the regions of a wafer where device formation will ultimately occur. Such regions might be formed locally or more commonly in a blanket/global manner relative to the substrate. Example embodiments of prior art methods are shown and described in U.S. Pat. No. 5,773,356, listing Fernando Gonzalez and Jeffrey W. Honeycutt as inventors, and which matured from a patent application filed on Feb. 20, 1996. The U.S. Pat. No. 5,773,356 is hereby incorporated by reference. Such depicts proximity gettering regions formed within and on the back side of semiconductor wafers by ion implantation. Such regions are typically formed to have their implant peak concentrations at least 3.0 microns from the front surface of the substrate at the time of implanting. Subsequent heating imparts elevational spread of the implanted regions from the peak beyond that which inherently occurs during the implant(s). The prior art has also formed surface proximity gettering regions locally right at the substrate front side surface.
The deeper the desired implant for a given species, the higher is the typicaI required implant energy and the current density to achieve the desired depth. Yet typically the higher the implant energy and the current density, the greater will be the elevational spread of the region (typically referred to as xe2x80x9cRp) as implanted and the greater the damage to the outer surface of the substrate. And, the greater the initial Rp, the greater will be the final Rp which inherently results from subsequent thermal processing of the substrate during manufacture. In many cases, it is desirable to minimize the Rp of proximity gettering regions, whether surface or buried within the substrate. This is expected to be of even greater significance in the expected ever smaller geometries of later generation integrated circuitry fabrication.
The invention comprises methods of forming semiconductive active area having a proximity gettering region and methods of processing monocrystalline silicon substrates to have a proximity gettering region. In one implementation, a method of forming semiconductive material active area having a proximity gettering region received therein includes providing a substrate comprising bulk semiconductive material. A proximity gettering region is formed within the bulk semiconductive material within a desired active area by ion implanting at least one impurity into the bulk semiconductive material. After forming the proximity gettering region, thickness of the bulk semiconductive material is increased in a blanket manner at least within the desired active area.
In one implementation, a method of processing a monocrystalline silicon substrate includes forming a proximity gettering region within monocrystalline silicon of a monocrystalline silicon substrate. After forming the proximity gettering region, epitaxial monocrystalline silicon is formed on the substrate monocrystalline silicon to blanketly increase its thickness at least over the proximity gettering region.